Purchasing activation codes via e-bay.

I purchsed a downloaded activation code from a verified e-bay seller.The code does not work giving the error code:
I also wondered why their advert claimed Windows 7 Home premium is the "most veratile" version of windows 7 O.S.
Romaurie

Manythanks for your reply.
The company just sent a new number that activated O.K.
There is a very large difference in local pices for the code, $127 and on line e-bay $28.I have the disc already with a Dell lap-top installation.
Romaurie